1. Field of the Disclosure
This disclosure relates to frame rate control unit and method adapted to enhance picture-quality, and a liquid crystal display device with the same.
2. Description of the Related Art
As the information society grows, display devices capable of displaying information have been widely developed. These display devices include liquid crystal display (LCD) devices, organic electro-luminescence display (OLED) devices, plasma display devices, and field emission display devices.
Among the above display devices, LCD devices have the advantage in that they are light, small, and can provide a low power drive and a full color scheme. Accordingly, LCD devices have become widely used for mobile phones, navigation systems, portable computers, televisions and so on.
The LCD device includes a timing controller transferring red, green, and blue (RGB) data from external video source to a data driver. The RGB data is converted in an analog data voltage and applied to a liquid crystal panel. The LCD device further includes a gate driver configured to drive gate lines on the liquid crystal panel.
In general, the RGB data applied to the timing controller consists of 8 data bits. As such, the data driver is configured to process the 8 bits of RGB data. However, the data driver capable of processing the 8 bits of RGB data is at a very high price. In view of this point, a data driving method capable of allowing the 8 bits of RGB data to be processed by a data driver with less than 8 bits is keenly required.
To meet this requirement, a frame rate control (FRC) method has been proposed which realizes the gray levels of at least one lower data bit among 8-bit RGB data by at least two continuous frames. The FRC method derives fewer bits of RGB data (for example, a 6-bit or 5-bit RGB data) than 8 bits from 8-bit RGB data. To this end, the FRC method reconfigures a first fixed number of higher data bits (for example, higher 6 or 5 data bits) among 8-bit RGB data in one set of several continuous frames on the basis of a second fixed number of lower data bits (for example, lower 2 or 3 data bits). The re-configured fewer-bit RGB data can be processed by a fewer-bit data driver than 8 bits.
Meanwhile, inversion systems have been proposed, in order to prevent the deterioration of liquid crystal. The inversion systems include a dot inversion, a line inversion, and a frame inversion. The dot inversion system can include a vertical 2-dot inversion and a horizontal 2-dot inversion.
FIGS. 1A and 1B are data sheets illustrating a FRC system using a horizontal 2-dot inversion. FIG. 1A is a data sheet showing a set of FRC patterns, and FIG. 1B is a data sheet showing one set of data frames obtained by applying a horizontal 2-dot inversion to the FRC patterns.
As shown in FIG. 1A, The FRC method can provide a set of FRC patterns every 4 frames. In this case, the FRC patterns can be obtained by applying a lower 2-bit data extracted from an 8-bit RGB data to one set of 4 continuous frames.
The four FRC patterns corresponding to the 4 continuous frames can be re-formatted in a horizontal 2-dot inversion, as shown in FIG. 1B. The horizontal 2-dot inversion system inverts the polarity of RGB data every two sub-pixels in the horizontal direction. If positive polarity sub-pixel data is applied to two sub-pixels in the horizontal direction, the following two sub-pixels in the horizontal direction is designated to receive negative polarity sub-pixel data. In this manner, the polarity of the sub-pixel data can be repeatedly inverted every two sub-pixels in the horizontal direction.
The four FRC patterns, to which lower 2-bit data extracted from 8-bit RGB data is applied and the horizontal 2-dot inversion is performed, allow the number of red sub-pixels receiving positive polarity data to be the same as that of the red sub-pixels receiving negative polarity data. They also allow the number of blue sub-pixels receiving positive polarity data to be the same as that of blue sub-pixels receiving negative polarity data, in every frame. For example, among the red sub-pixels marked by diagonal lines in a first frame of FIG. 1B, the number of red sub-pixels receiving the positive polarity data is equal to that of red sub-pixels receiving the negative polarity data, as 4.
However, the number of green sub-pixels receiving the positive polarity data among the green sub-pixels is larger than that of green sub-pixels receiving the negative polarity data. For example, among the green sub-pixels marked by diagonal lines in a first frame of FIG. 1B, the number of green sub-pixels receiving the positive polarity data is “8”, but the number of red sub-pixels receiving the negative polarity data is “0”. On the other hand, this polarity arrangement is the same as those in a second to a fourth frames. As all of the green sub-pixels respond to the positive polarity data, defects such as flickering, noise, dimness, and others are generated in the picture displayed by the LCD device. The picture quality of the LCD device is deteriorated.